Aluminum Armor Plate Good Enough for Humvees

The US Army Research Lab has specified Alcoa's latest armor material for use on US military vehicles. After testing Alcoa's ArmX 5456-H151 armor plate on the Army's Fuel Efficient Ground Vehicle Demonstrator (FED) vehicle, the lab found that it is stronger than baseline weldable armor plate and has better blast and ballistic performance.

Alcoa's aluminum and armor products have been used in military vehicles for decades, including Humvees and the Bradley Fighting Vehicle. The ArmX brand of weldable aluminum alloy armor plate was developed originally for aerospace applications, and is known for strength and toughness in both plate and forgings. The materials are based on the proprietary 7085 alloy. Their thermal and forging properties are tailored to survive blasts better and to weigh a lot less than steel armor made for similar levels of blast-threat survivability. The new material was found to be 20 percent stronger than the baseline 5083-H131 alloy plate material, said Mark Vrablec, Alcoa's president of global aerospace, transportation, and industrial rolled products, in a press release.

Alcoa's newest weldable armor plate alloy is now specified by the US Army Research Lab for use in military vehicles, including Humvees. The ArmX 5456-H151 armor was demonstrated on the Army's Fuel Efficient Ground Vehicle Demonstrator (FED) Alpha version, shown here. The FED vehicle's various lightweighting and efficiency technologies let it get 70 percent better fuel efficiency than a Humvee. (Source: Alcoa/US Army)

ArmX 5456-H151 armor panels come in forgings of a wide range of sizes and geometries and in thicknesses ranging from 0.5 to 4 inches. The panels can be used in applications such as land vehicle hatches and doors, turrets, armor underbody blast shields, wheel coverings, and roof or side panel window frames. They are also being used in naval marine applications such as lightweight blast protection panels for command centers and other personnel enclosures.

The new material was tested on the Alpha version of the Army's FED vehicle. Alcoa helped develop this prototype vehicle for demonstrating lightweight, fuel-efficient technologies that are also durable enough to protect military vehicles and to ensure the safety of troops traveling in them. The vehicle's lightweight structure cuts fuel consumption by 6 to 7 percent and reduces its weight by as much as 10 percent compared to a similar-sized vehicle made from steel. That may not seem like a big improvement in fuel consumption, but the FED weighs 15,000 lbs. and only gets 7 mpg. Yet it can zoom along at speeds of up to 75 mph.

The vehicle is housed along with the other model, FED Bravo, at the Army's Tank Automotive Research, Development, and Engineering Center (TARDEC). Both were designed to perform similar tasks as a Humvee, but they can do so with 70 percent better fuel efficiency.

The Alpha version has an armored cab made of Alcoa's lightweight aluminum alloys, including an underbody blast shield, as well as low-drag aluminum brake calipers. It's also equipped with Goodyear low-rolling-resistance tires to decrease wasted energy created as heat between the road and the tire, and body panels made from carbon-fiber-reinforced composites to help lighten it up and also maintain rigidity.

The article mentioned brake calipers. Several years ago, I worked on a project with TARDEC to replace cast-iron brake calipers with high-strength aluminum brake calipers for a military vehicle (not this one). Doing so reduced the vehicle weight by literally hundreds of pounds.

I'm not sure where that project went, since I left the company soon after. My lab technician went on to get a master's degree out of the experience, while I'm still working (slowly!) on mine.

The idea of using aluminum alloys to make arm or plates is, in my view, particularly important because of 2 reasons. First, we all know that aluminum weighs a lot less than speed. Thus the humvees will be lighter and easier to transport. The greater strength of this allow is also great for battlefront scenarios. But, on the downside, the reduced weight means that other reinforcements have to be added if it is to withstand blasts without flipping the humvee.

Regarding both the 7085 alloy and possible armor construction, here's a 2002 press release describing the "new" alloy's use in blast-resistant (note that's *not* blast-proof) Fortress cargo containers for airlines:http://www.alcoa.com/global/en/news/news_detail.asp?newsYear=2002&pageID=222034673"The Fortress Container uses hardened aluminum alloys for both the frame and skin.""The aluminum container structure is designed to resist pressure loads from an explosion, while an interior Kevlar lining provides protection from blast fragments. In designing the Fortress Container, Alcoa used its experience gained in developing aluminum armor for the Bradley Fighting Vehicle, the HMMWV (Humvee) and other military applications."How much this tells us about the armor plates, vs the cargo container panels, is an open question, but it sounds like their construction is similar.Here's some detailed info about the alloy. I couldn't extract the link, but if you Google this it should come up:ALCOA_7085-T7452_Die_Forging_green_letter_Ed_3_August_2006.pdf

The U.S. Navy also experienced problems with aluminum when the USS Stark (frigate ship) was struck by two Exocet missiles in the Persian Gulf in 1987...killing 37 sailors. The aluminum melted in many places affected by fire, including aluminum stairs and ladders, hampering escape and damage control.

All aluminum has a rather low melting point of around 1,200 degrees F (660 deg C), and the mechanical properties of aluminum are severely compromised by temperatures of only 400 degrees F (205 deg C).

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